Division mechanism-pre-estimation



Sept. 14, 1954 H. T. AVERY 2,689,085

DIVISION MECHANISM-PRE-ESTIMATION OF QUOTIENT DIGITS BY DIVIDEND-DIVISOR COMPARISON Filed April 24, 1950 15 Sheets-Sheet l QQQO Q Q Q Q Q Q Q Q Q Q A e E NT Sept. 14, 1954 H AVERY 2,689,085

T. DIVISION MECHANISM-PRE-ESTIMATION OF QUOTIENT DIGITS BY DIVIDEND-DIVISOR COMPARISON 13 Sheets-Sheet 2 Filed April 24, 1950 Sept. 14, 1954 AVERY 2,689,085

DIVISION MECHANISMFIRE-ESTIMATION OF QUOTIENT DIGITS BY DIVIDEND-DIVISQR COMPARISON Filed April 24, 1950 13 Sheets-Sheet 3 I N V EN TOR.- Ham/d, T Avery AGENT H. T. AVERY Sept. 14, 1954 2,689,085 DIVISION MECHANISM-PRES-ESTIMATION OF QUOTIENT DIGITS BY DIVIDEND-DIVISOR COMPARISON 1950 13 Sheets-Sheet 4 Filed April 24 IN VEN TOR: Ha ro/d 7' Avery (II/AIQ ,nummnm: null Sept. 14, 1954 AVERY 2,689,085

DIVISION MECHANISM-PRE-ESTIMATIQN 0F QUCTIENT DIGITS BY DIVIDEND-DIVISOR COMPARISON Filed April 24, 1950 13 Sheets-Sheet 5 R. w w m VT m m %E fl M w I IA Y 1 B H. T. AVERY Sept. 14, 1954 2,689,085

DIVISION MECHANISM-PRE-ESTIMATION 0F QUOTIENT DIGITS BY DIVIDEND-DIVISOR COMPARISON Filed April 24, 1950 13 Sheets-Sheet 6 Q NR A s EMT Sept. 14, 1954 H. T. AVERY DIVISION MECHANISM-PRE-ESTIMATION OF QUOTIENT DIGITS BY DIVIDEND-DIVISOR COMPARISON Filed April 24, 1950 15 Sheets-Sheet 7 INVENTOR. Hare/d T/ll/erz 4 322 FlE LE Aer-z NT Sept. 14, 1954 H, AVERY 2,689,085

DIVISION MECHANISM'PRE-ESTIMATION OF QUOTIENT DIGITS BY DIVIDEND-DIVISOR COMPARISON Filed April 24, 1950 13 Sheets-Sheet 8 INVENTOR: flaw/d TAl erz A6 E. NT

Sept. 14, 1954 H T AVERY 2,689,085

DIVISION MECHANISM PR E-ESTIMATION OF QUOTIENT DIGI'IS BY DIVIDEND-DIVISOR COMPARISON Filed April 24, 1950 13 Sheets-Sheet l0 INVENTOR:

Hare/d T Ayer'z A GENT Sept. 14, 1954 H. T. AVERY DIVISION MECHANISM-PRE-ESTIMATION OF QUOTIENT DIGITS BY nzvxmzwunzvrsma COMPARISON 13 Sheets-Sheet 12 Filed April 24, 1950 r m m lqh NHQQQ QZQUMM NUQQQ kqmm x I N V EN TOR: Ham/d TAverl AGENT H. T. AVERY DIVISION MECHANISM-PRE-ESTIMATION OF QUOTIENT DIGITS BY, DIVIDEND-DIVISOR COMPARISON 13 Sheets-Sheet 15 Filed April 24, 1950 QEE a: mo $53 muam Quit I N V EN TOR: f/aro/d Z Avery AeaN-r Patented Sept. 14, 1954 DIVISION MECHANISM-PRE-ESTIMATION OF QUOTIENT DIGITS BY DIVIDEND- DIVISOR COMPARISON Harold T. Avery, Oakland, Calif., assignor to Marchant Calculators, Inc., a corporation of California Application April 24, 1950, Serial No. 157,818

Claims. 1

The present invention relates to calculating machines and particularly concerns pre-estimation short-cut division mechanisms. The preestimation mechanism of the present invention is capable of comparing the divisor with either the true (positive) value of the dividend remainder or the complemental '(negative) value thereof, and on the basis of such comparison, automatically estimates the corresponding value of the current quotient digit to substantially the nearest full integer; and in accordance with well known principles of short-cut calculations the quotient digit thus estimated is registered by substantially the minimum number of plus or minus operations of the numeral wheel actators.

The machine in which the present invention is embodied, is disclosed in application Serial Number 12,232, filed March 15, 1948, now Patent No. 2,567,120, issued September 4, 1951, and the machine of that patent is characterized by mechanism which makesit possible to eiiect and complete a shifting operation during the operation of the numeral wheel actuators in multiplication calculations. In performing division calculations on that machine, however, it is necessary to delay the shift until the machine has determined whether or not an overdraft has occurred; whereas, according to the present invention, comparison on the basis of true and complemental values and the registration of the estimated quotient digits by selective plus or minus operations, make it possible to take full advantage of the simultaneous shift and actuation feature in division as well as multiplication.

The present invention is therefore based upon the principle of comparing a divisor with either the true or complemental value of a dividend remainder, estimating a corresponding quotient digit, and registering the same by substantially a minimum number of plus or minus machine cycles.

A primary object of the present invention is, therefore, to obtain the quotient of a division problem in substantially the minimum number of cycles of machine operation.

Another object is to compare the divisor with the negative or complemental value of the dividend remainder and estimate the corresponding quotient digit, to thereby control registration of said digit by the short-cut method.

Still another object is to sense the value and sign of the dividend, or remainder thereof, and

in accordance with said sign to selectively enable one of two pre-estimating devices to compare either a positive or negative remainder value with Cir 2 the divisor and thus obtain the value and sign of the corresponding quotient digit.

Another object is to determine the value standing in a crawl carry register by sensing the rotated position of one or more ordinal value representing members and to eliminate the effect of any backlash in the crawl carry register upon the determination of said value.

A still further object is to shift the divisor storage mechanism relative to the dividend register during an ordinal division operation involving either positive or negative registration of the numeral wheels, and to initiate the succeeding ordinal division operation upon conclusion of such registration.

Other objects and advantages will become apparent from the following detailed description of the invention, in which:

Fig. 1 is an exterior plan view of the calculating machine embodying the present invention.

Fig. 2 is an enlarged isometric projection of the primary pre-estimating mechanism asseen from the right rear of the machine.

Figs. 3 and 4 are schematic illustrations showing the movements imparted to various parts of the primary pre-estimator during diiierent quotient pre-estimating operations.

Fig. 5 is a sectional view of the dividend value representing lever and related mechanisms taken along line VV in Fig. 2.

Fig. 6 is an enlarged detail view of part of the dividend sensing control mechanism as viewed from the right side of the machine.

Fig. 7 is an enlarged isometric projection of the mechanism for compounding the values sensed in the three highest orders of the dividend, as seen from the right rear of the machine.

Fig. 8 is a sectional view of part of the compounding mechanism shown in Fig. 7 as seen from the rear of the machine.

Fig. 9 is an enlarged isometric projection of the complementary pre-estimating mechanism as seen from the right rear of the machine.

Fig. 10 is a right side view, partly in section, taken along line X--X in Fig. 1 showing the general arrangement of some of the component parts of the machine.

Fig. 11 is a right side View, partly in section, showing the main clutch and the control mechanism for the centralizer pawls of the dividend and quotient registers.

Fig. 11A is a sectional view as seen from the right side of the machine showing a portion of the main clutch control mechanism.

Fig. 12 is a right side view of part of the division control mechanism.

Fig. 13 is an isometric projection as viewed from the right rear of the machine, showing parts of the division initiating mechanism.

Fig. 14 is a right side view of the divison start key and division terminating mechanisms.

Fig. 15 is a right side view of the mechanism for moving the dividend sensing mechanism into and out of operation.

Fig. 16 is a plan view of a portion of the dividend and divisor sensing mechanism.

Fig. 17 is a right side view of the shift clutch and the drive train for shifting the dividend sensing carriage and the divisor storing carriage.

Fig. 18 isa detailed right side view of part of the shift drive train shown in Fig. 1'7.

Fig. 18A is a detailed right side view showing the mechanism which is operable in the last order of division to disable the shift drive train.

Figs. 19 and 19A is a right side view of the mechanism for controlling a switch that cuts in the pre-estimation circuit and cuts out the terrninating clutch solenoid, and vice versa.

Fig. 20 is a wiring diagram showing the various electrical controls used in division operations.

Figs. 21 and 21A form a timing diagram showing the sequential operation of the division mechanisms during the performance of a typical division problem.

GENERAL DESCRIPTION The machine of the aforementioned Patent No. 2,567,120 includes a plurality of ordinally arranged differential actuators, one permanently associated with each respective ordinal numeral wheel of the accumulator register so that there is no need for causing relative shifting between the actuators and accumulator in order to effect the entry of values into various orders of the accumulator.

A shiftable numeral value storage mechanism, having a lesser number of orders than there are ordinal actuators, is set by the numeral keys of the keyboard, and in turn, sets the ordinal actuators with which it is aligned so that the actuators drive the numeral wheels by the amounts set in the respective orders of the value storage mechanism. The setting of the actuators in each order is maintained throughout an ordinal registering operation, and during such operation the storage mechanism may be shifted to its next ordinal position in preparation for resetting the actuators at the beginning of the next registering operation. The shifting of the storage mechanism does not affect the last setting of the actuators; therefore, a shifting operation occurs during the registering operation without delaying the successive operations of the actuating mechanism.

The division mechanism of the present invention is so arranged that at the end of a registering operation in one order, the machine immediately starts the succeeding ordinal division operation without any delay for shifting of the storage mechanism to change the ordinal relation of the divisor to the dividend.

In performing a division problem the dividend is first entered into a factor indicator 102 (Fig. 1) by depressing the numeral keys Il-H9. The dividend entry (a key I26 is then depressed to transfer the selected dividend value from the indicator I02 into the dividend register I00 and also to effect clearance of the factor indicator I02. The divisor is then entered into indicator I02 by depressing the corresponding numeral keys, and

4 upon depression of the division start or equals key I28, automatic division is initiated, during which the dividend and divisor values are compared by the mechanism which comprises a part of the present invention, to estimate and then register the quotient in register I0l.

ENTRY MECHANISM The entry mechanism includes a shiftable multi-order value storing carriage 30] (Fig. 10) which receives and stores the values entered by the depression of the numeral keys |l0-l l9 (Fig. 1). Such entries are made from left to right beginning with the leftmost order of factor indicatorl02.. One order of the storing carriage MI is shown in Fig. 10 and which order comprises ten blocking levers 3 0-3 I 9.

Depression of a numeral value key rocks a respective one of the blocking levers 3l0-3l9 counterclockwise, where it remains throughout the division operation. Concurrent with such movement of a blocking lever, a respective ordinal numeral wheel 23! of the factor indicator I02 is rotated to a position to show the value selected in that order. The numeral keys are successively depressed until the entry of a factor is completed at which time the factor indicator I02 shows the value entered, and respective ones of the ordinal rows of blocking levers 3|0-3l9 are rocked to positions in which they later effect engagement of respective numeral wheel clutches, described hereinafter.

Reference may be had to the previously mentioned patent for a complete description of the mechanism for entering a value into the factor indicator I02 and the storing carriage 301.

NUMERAL WHEEL ACTUATORS There is a row of ten numeral wheel clutches 400 (Fig. 10) for each dividend register numeral Wheel [0 and the above mentioned blocking levers are each effective to control the engagement of a respective one of these clutches. The drive element of each clutch 400 is fixed on a respective drive shaft 350-359, each of which is rotated a diiferent amount during each cycle of operation of a main clutch described hereinafter. When a numeral wheel clutch 400 is engaged, it transmits a respective differential drive to an associated numeral wheel l0 of the dividend register. For this purpose the driven element of each clutch carries a respective gear 390-399 (Figs. 10 and 11) and each ordinal series of gears 390499 is enmeshed to form an idler gear train. Entrained with the idler gear train is a drive receiving gear 40l journaled on a shaft 402. The drive from gear MI is transmitted to an associated numeral wheel l0 through a crawl carry gearing (Fig. 11) described hereinafter.

During multi-order operations such as division, which require changing the ordinal relationship between the divisor factor and the dividend or its remainder, the storing carriage 30! (Fig. 10) is shifted one order toward the right during each ordinal actuating operation to associate the divisor factor set therei-n with the successively lower orders of the numeral wheel clutches 00.

The storing carriage 30.! carries a worm nut 303 (Fig. 10) which is driven by a worm shaft 308. This shaft is rotated by a shift clutch described hereinafter to cause ordinal shifting of the storing carriage. During such shifting movement each previously engaged numeral wheel clutch 400 is adapted to be held in engaged position, so that numeral wheel actuation is not affected by the shift of the storing carriagaall as is fully described in said patent.

From the foregoing description of the entry mechanism and numeral wheel actuators, it will be apparent that the provision of the same or substantially the same number of orders in the actuating mechanism as there are orders in the accumulator, together with the provision of a multiorder carriage which receives and stores a multiorder factor and which is shiftable ordinally relative to the actuators, makes it possible to set a factor into any group of orders of said actuating means. Since the engagement of the numeral wheel clutches 400 is maintained during an actuating operation, the storing carriage may be shifted into its next ordinal position during such operation; therefore, successive ordinal operations of the actuators may be effected without any delay for the ordinal shift.

DIVIDEND REGISTER 19, 1949, now Patent No. 2,622,805, issued December 23, 1952.

Each numeral wheel l0 (Fig. 11) of this register is advanced by a respective planetary gearing generally indicated at andwhich planetary comprises a digital input gear 2|, an internal ring gear 26, a tens carry input gear 22', and a summation gear [8. The summation gear i8 is advanced in accordance with the sum of the digital and tens carry increments entered through gears 2|, 20, and 22' and drives the numeral wheel I0 through a rockable idler I4.

At the end of a calculation the idler gear I4 is rocked clockwise a selective amount inthe manner described in the last mentioned Patent No. 2,622,805 to back out partial carry increments and thus align the numeral wheel in a full digital position.

The register I00 differs from conventional crawl carry registers in that the aligning movement of a numeral wheel I8 is accomplished without moving the summation gear [8' of the differential 20. The snail cam 402 (Fig. 10) which is integral with gear 18', thus stands in the crawl position regardless of the aligning movement of the respective numeral wheel. The rotated position of any snail cam 482 therefore may be sensed previousto or during the aligning of the numeral wheels to determine the value standing in the dividend register I00 without the aligning movement afiecting the value sensed. In the machine of the present invention, a divided sensing occurs previous to each pre-estimation operation, and is effective to adjust the quotient pre-estimating mechanism in accordance with the values sensed.

, The dividend sensing mechanism includes a plurality of follower levers 483 (Fig. 10) each of which is adapted to rock counterclockwise and contact the graduated periphery of a respective snail cam 482. The rocked position of a lever 483 is then sensed by means described hereinafter to determine the value standing in that order. Levers 483 are keyed for limited angular movement on the shaft 402, and during the sens ing operation they are spring urged into contact with their aligned snail cams 482.

During an actuating operation, the levers 483 must be held clear of their respective snail cams to prevent interference between the levers and the rotated cams. This is accomplished as follows. A cam 6l8 (Fig. 11), driven by a setting clutch, described hereinafter, operates previous to each actuation and rocks a follower lever 488 clockwise about pivot 489. The upper arm of lever 48B is pivotally connected to the right end of a link 481. At its left end, link 40! is pivotally connected to a lever 484 which is secured to shaft 402. The follower levers 483 (Fig. 10) as previously mentioned, are loosely keyed to this same shaft 402. The clockwise movement imparted to follower 488 (Fig. 11) rocks shaft 402 clockwise sufiiciently to move the follower levers 483 out of the paths of their snail cams 482 and levers 483 are locked in this position throughout the actuating operation as follows.

A latch 40! (Fig. 11) is freely mounted on shaft 492 and is held in the clockwise position shown by the contact of an arm 494 with a pin 4901 on the latch 491. Arm 494 is fixed to a shaft 508 which carries a main clutch control dog 5H5. During the setting clutch cycle a setting clutch cam Bill and a follower 63| rock the shaft 508 clockwise to cause engagement of a main clutch 5i5 described hereinafter. This clockwise movement of shaft 508 also rocks arm 494 clockwise thus permitting the latch 4% to be rocked counterclockwise by its spring and engage ear 480a on follower lever 488, which has previously been rocked to a clockwise position by cam 618. The latch lever 49l holds the follower lever 488 in its clockwise position as long as the main clutch dog 5H5 is held in clutch engaging position. The setting clutch completes itscycle of operation and is disengaged during the first cycle of operation of the main clutch, but such disengagement does not affect the above described latch lever 49!. In this manner shaft 402 isrocked clockwise and the follower levers 483 (Fig. 10) are held in positions away from the snail cams 482 throughout the actuating operation and until the main clutch dog rocks to clutch disengaging position. At such time the arm 494 (Fig. 11) on shaft 402 removes the latch 40! from a restraining engagement with ear 488a, thus permitting the counterclockwise movement of lever 488 and the return of the follower levers 403 (Fig. 10) to engage the peripheries of their respective snail cams 482.

The above mentioned clockwise movement of shaft 402 is also effective through the connecting linkage comprising arm 748, link I50, lever 15!, link I52, and arm 153, to move the ordinal numeral wheel centralizer awls 30 and T55 of the dividend and quotient registers respectively out of engagement with gears 20 and M8. In this manner the pawls are held in disengaged position throughout the operation of the main clutch and are released from disengaged positions at the end of an actuating operation to centralize their respective numeral wheels [0 and 70! at the same time the follower levers 483 are released to contact the snail cams 482.

QUOTIENT REGISTER The quotient register lfll (Figs. 1 and 11) is of the crawl carry type disclosed in they aforementioned Patent No. 2,567,120, and with the exception of the manner in which the numeral wheels are aligned it is generally similar to the accumulator or dividend register M0.

The register |0l includes the numeral wheels '30! (Fig. 11), each of which is driven by a respective drive gear 103 through a planetary gear train generally indicated at 102. Each gear 103 is driven by a respective ordinal clutch similar to the ordinal clutches 400 of the actuating patent.

emsaoss mechanism for thedividend register,-there being only one clutch 1023 for each order of the counter register in contrast to the plurality of clutches 400 for each order of the dividend register.

A shiftable interponent l I 6, which is similar'in operation to the blocking levers 310-3 I 9 (Fig. 10) of the storing carriage 30'], is provided to cause engagement of one of the ordinal counter numeral wheel clutches 100 (Fig. 11) as described in said The arrangement is such that engagement of a clutch 100 causes a single count to be entered into an order of the counter register during each cycle of operation of the actuating mechanism.

The interponent H6 has a driving engagement with a worm shaft 1 IS for shifting of the interthe multi-order divisor factor is added to or subtracted from the dividend numeral wheels and thereby register the quotient digits.

For a more detailed description of the quotient register and the manner in which the numeral wheels thereof are advanced to indicate the quotient, reference may be had to said Patent No. 2,567,120.

MOTOR DRIVE MECHANISM The motor drive mechanism of the present machine includes an electric motor from which five separate drive trains are provided through a setting clutch, a main clutch, a shift clutch, a terminating clutch and a clear clutch, respectively.

The drive trains to the setting clutch, the main clutch, the shift clutch and the clear clutch are the same as described in the last mentioned patent; whereas, the drive to the terminating clutch is described hereinafter. It will be noted with reference to Fig. 20, that the movement of any one of the respective clutch control dogs for these five clutches to clutch engaging position is effective to close a respective switch in a corresponding circuit from the main line 9H and lead 29! to the motor 501. The motor circuit remains closed until the respective clutch dog moves to clutch disengaging position.

The above mentioned clutches and the respective cams and the associated mechanisms driven by these clutches are designated in the specification and in the drawings as follows: S. C. for setting clutch, M. C. main clutch, Sh. C. for shift clutch, C. C. for clear clutch, and T. C. for terminating clutch.

Setting clutch The setting clutch (not shown) operates, as described in the last mentioned patent, to drive a sleeve 6|! (Fig. 11) which has various cams fixed thereto including the previously mentioned cams H3 and BIB. A setting clutch cam BIB, shown diagramatically in Fig. 20, closes a switch 630 in the circuit of a shift clutch solenoid 559 to cause energization of that solenoid. Each ener gization of the shift solenoid initiates a shifting operation, asdescribed in said patent.

Two setting clutch cams (not shown) are provided in the present machine to cause engagement and disengagement respectively, of the numeral wheel clutches 400 (Fig. 10) in accordance with the setting of the previously mentioned blocking levers Sill-BIB. Another setting clutch cam is provided to condition a control mechanism for the actuating mechanism. These three cams are identified by the reference numerals 6I5, SIB and 6|! in said Patent No. 2, 567,l20 and while not shown in the present application it will be understood that they perform the same functions as described in that patent.

Shift clutch The shift clutch 550 (Fig. 17) operates werfect ordinal shifting movement of some of the component partsof the machine including the selectionstoringcarriage 31" (Fig. 10) and the ordinal counter control interponent 1 16 (-Fig. 11) as wllas various shit-table elements or the division control mechanism, described hereinafter. The shift clutch 650 (Fig. 17) is a half revolution clutch and correspondsto the clutch of'the same reference numeral in the last mentioned patent. Each cycleof operation of the half-revolution shift clutch drives-a'sleeve 553a (Fig. 17) and its two cams 555 (Fig. 15) and 561 (Fig. 17) a full revolution.

Cam 561 forms a partof the mal'n shift drive *train of the machine and, with 'other associated mechanisms, serves to advance the shiftable parts of themachine one step for *each cycle of the shift clutch, while cam' fifii serves torestore "the dividend sensing mechanism to its initial "nonsensing position.

Cam 56'! operates through a follower 568 (Fig. 18) and an actuating pawl 569 toadvance a shift ratchet EH onestep counterclockwise for each cycle of the shift clutch. A pawl 512 engages successive teeth of ratchet 5' to hold the latter in its advanced positions. Each time the ratchet 511 is advanced one step, various ordinally shiftable elements of the machine are shifted one order. These elements include the selection storing carriage 301 (Fig. 10) shiftable by means of the worm shaft 308, (Fig. 10) and the counter concurrently with the actuating operation or as a result of a 0 quotient estimation. The selection storing carriage and the counter interponent must not be shifted beyond their last ordinal positions of alignment with their respective "ordinal actuators, however, since the last ordinal estimation and actuation may leave a negativeremainder in the dividend register in which case a corrective plus stroke must be initiated by the terminating mechanism. The shift ratchet 51! (Fig. 18) therefore carries adeflector plate 344 which, in the advancedposition shown in Fig. 18A, defiectsthe actuating pawl 569 to prevent further advance of ratchet 5' during the additional shift clutch cycle. This deflector plants also serves to prevent advance of the ratchet 5' during the terminating clutch cycle in those cases where a corrective plus stroke and concurrent shifting operation is initiated.

The follower arm 568 (Fig. 19) carries a second actuatingpawl 569a which advances a second ratchet 51m in much the same manner as the actuating pawl 569 advances ratchet 5' (Fig. 18). Ratchet and is fixed to a'cam 310 which, "in the position of the ratchet and cam shown in Fig. 19A, is effective to open switch 686 (Fig. 20) in the pre-estimation control circuit and to close switch 369 in the circuit of a terminating clutch solenoid 36L Ratchet 51m and its cam 3'10 (Figs. 19 and 19A) however, are

arranged to be advanced one step more than ratchet 51! before closing switch 369 and opening. switch 685. After such an additional step of advance, the ratchet 51 la is blocked from further operation by the shift clutch and the actuating pawl 569a, in order to hold switch 369 closed and switch 686 open. The ratchet 5'Ha is therefore provided with a deflector plate 344a similar in all respects to plate 344, except that plate 344a is so located as to lag one step behind the plate 344 and to block advance of ratchet 511a one shift clutch cycle later than that in which ratchet 51! is blocked.

The ratchets 5H and 51|a are yieldably connected so that when the ratchet 5' is returned to its initial position by the clear clutch as described hereinafter, the ratchet SHa will likewise be returned to its initial position. An ear 688 (Fig. 18) on ratchet 5' lies adjacent an ear 689 (Fig. 19) on ratchet 5H and a torsion spring 690 passes through each ear and around the shaft as shown in Figs. 19 and 19A to urge the two ears against each other. When the ratchet 51Ia is advanced one step farther than the ratchet 51! the torsion spring 690 yields and the parts assume the respective positions shown in Figs. 18A and 19A.

During a clearance operation, described in the previously mentioned Patent No. 2,567,120, a clearance control member (not shown) contacts ear 572a (Figs. 18 and 18A) of the holding pawl 512 and rocks the latter counterclockwise out of restraining engagement with ratchet 5H. At the same time a pin 512?) on a third arm of the holding pawl 512 rocks the actuating pawl 569 out of the path of the ratchet 51 l. The latter thereupon is rotated clockwise by spring means disclosed in said patent to drive the shift train in the opposite direction from which it is advanced by the shift clutch and to return the members previously shifted by said clutch back to their initial positions.

In the present invention a new ear 69I is provided on the holding pawl 512 and which ear is adapted to rock the holding pawl 512a (Fig. 19) counterclockwise. This releases ratchet 511a from the holding pawl 512a and permits it to follow the ratchet 5H and return to the initial position shown in Fig. 19.

Main clutch The main clutch 5| 5 (Fig. 11 drives through a suitable train of gears described in the previously mentioned Patent No. 2,567,120 to rotate the differential actuator shafts 35I-359 (Figs. and 11) by amounts proportionate to the values 1 to 9. Shaft 35!] is the O shaft and is locked against rotation to prevent driving of the dividend register numeral wheels in those orders where a 0 has been selected.

The main'clutch also serves through a suitable drive train, shown in said patent to drive the ordinal gears "me (Fig. 11) through one of the quotient numeral wheel clutches 700 and enter a single increment of count into a selected order of the quotient register llll during each cycle of operation of the main clutch.

The clutch control dog 516 (Fig. 11) for the main clutch 515 is rocked to clutch-engaging posi tion by the setting clutch cam 6 I 3 previously men tioned, and is held in clutch-engaging position by a latch (not shown). The latch and its related control devices, which are all fully described in the last mentioned patent, are operable to hold the main clutch dog in engaged position for a predetermined number of cycles of operation of the main clutch. Such operation of the latch is under the control of a series of electromagnets described hereinafter to cause disengagement of the main clutch after selective operation thereof through one to ten cycles.

Drive Reverse mechanism A main reverse drive unit is selectively operable to reverse the direction of rotation of shaft 524 (Fig. 10) and thereby reverse the drive from the main clutch to the actuator shafts 35l-359 for the clutches 400 and also to reverse the drive to the drive "shaft H15 (Fig. 11) for the clutches of the quotient register. The direction of rotation of shaft 524 is under control of a M. R., main reverse, solenoid 533, diagrammatically illustrated in Fig. 20. When the solenoid is de-energized the machine is conditioned for positive actuation of the dividend numeral wheels and when it is energized the machine is conditioned for negative actuation, as described in the above mentioned patent. A second drive reverse unit is operable in the di vision operations under the control of a quotient reverse solenoid 749 (Fig. 20) to reverse the drive from the above mentioned shaft 524 (Fig. 10) to the counter register drive shaft and thereby effect a positive count of the number of negative cycles of operation of the main clutch or vice versa. The above mentioned drive reverse units are conventional and reference may be had to the above mentioned patent for a description of parts not specifically described herein. The respective controls for these reverse units are more fully described in the section on division operations.

Clear clutch A clear clutch is provided to zeroize the numeral wheels in all or selected ones of the registers and indicators by operation of the various clear keys (Fig. 1) and the mechanisms controlled thereby. The olear clutch is also encaged as a result of a dividend entry operation. to return the selection storing carriage 30! (Fig. 10) and related selection mechanisms to their initial positions and also to clear the storing carriage of any value set therein, all as is fully described in the Patent No. 2,567,120.

Terminating clutch After the last ordinal division operation a single cycle terminating clutch 235 (Fig. 14) is automatically engaged as described hereinafter and performs two functions: (1) it causes selective initiation of a plus stroke in case the dividend remainder is a negative (overdrafted) value after the last ordinal division operation and, (2) it drives various cams which normalize the machine in preparation for the next calculation, all as is fully disclosed in a following section on the division mechanism. The drive for the terminating clutch is derived from the electric motor through a gear 236 (Fig. 15) fixed to'the main drive sleeve 5H, and this drive is transmitted through idler gears 238, 239 and 24!] to a gear 24! fixed to shaft 242. This shaft carries a drive ratchet 243 (Fig. 14) for the single cycle terminating clutch 235 and when the clutch is engaged, it drives a tubular shaft 245 and a plurality of camscarried thereby for performing the above terminating operations. Clutch engagement is causedby a terminating clutch solenoid 36I (Figs. 14 and 20) which, upon energization thereof, rocks clutch-dog 244 to clutch engaging position, and energlzation of this solenoid is controlled by mechanism described hereinafter in connection with division operations.

DIVISION MECHANISM The division mechanism includes means for initiating and automatically carrying out preestimation short-cut division operations, and also includes means for terminating thedivision operation with a positive remainder, if any, in the dividend register.

The means for automatically carrying out the division operation includes a quotient pre estimating mechanism which is described in the subsection immediately following. The division initiating and terminating mechanisms are described hereinafter.

Pre-estimating mechanism The pre-estimating mechanism of the present invention comprises two pre-estimating devices. The first will be referred to hereinafter as the primary pre-estimator which compares the value of the dividend or remainder thereof with the divisor to estimate the true or positive value of the current quotient digit, and the second will be referred to as the complementary or secondary pie-estimator which compares the complement of an overdrafted or negative remainder value with the divisor to estimate the current quotient digit. These two pre-estimating devices are selectively enabled or disabled in accordance with the sign of the dividend, or remainder. If the sign of the current dividend remainder is positive, then the primary preestimator is enabled and itexercises control over the number of minus cycles of operation of the actuating mechanism, while if the sign of the current dividend is negative, then the complementary pre-estimator is enabled to exercise control over the number of plus cycles of the actu ators.

Since the primary and complementary preestimators are generally similar in mode of operation, only the primary pre-estimator will be described in detail, such description also sufficing for the complementary pre-estimator except for minor differences which are pointed out hereinafter.

Briefly, the primary pre-estimator shown in Fig. 2 comprises a dividend lever I4I, freely mounted on a shaft 230 and adjusted along a dividend scale in accordance with the value of the current dividend, and a divisor lever I42, freely mounted on a stud I40 and adjusted along a divisor scale in accordance with the value of the divisor. In the position of the parts shown in Fig. 2 the dividend lever I4I stands at its initial position. The divisor lever I42 on the other hand stands at a position of approximately 8, and assumes this position when the pre-estimation mechanism is disabled because of the force of gravity on the particular form of the linkages shown to illustrate this invention, but when the rare-estim ion me anism is enabled, lever I42 is accurately set along the divisor scale at a position represent- 12 ative of the divisor value, as will presently appear.

The dividend and divisor levers, through connecting linkages, described shortly hereinafter, constrain a quotient bellcrank I43 to selectively close one of a series of eleven quotient switches I50-I6I] in accordance with the ratio (Du/Dr) of thedividend to the divisor. Usually only one quotient switch is closed at a time, but, in those cases when two adjacent switches are closed, the lower numbered switch controls.

The dividend and divisor levers MI and I42 jointly control the quotient bellcrank I43 as follows. The dividend and divisor levers have'respective depending links I44 and I45 freely pivoted thereto and which links are pivotally connected to'one another by a pin I 46. A link I41 is also pivotally connected to pin I46 and which link, at its opposite end is freely pivoted to the rightmost end of the quotient bellcrank I43. The latter is freely mounted on a shaft I48 suitably carried by the machine framework. The movements of the dividend and divisor levers along their respective dividend and divisor scales jointly position the pin I46 which, through link I41 constrains bellcrank I43 to move clockwise and close one of the switches I50I60 representative of the ratio Dv/Dr.

In the schematic illustration shown in Fig. 3, for example, the dividend lever I4I stands at a value of 24 and the divisor lever I42 stands at a value of 6, thus moving respective links I44 and I45, pin I46 and link I41 to positions in which link I41 constrains the quotient bellcrank I43 to close the #4 quotient switch. In Fig. 4 the dividend leverI4I stands at a value of 28 and the divisor lever I42 stands at a value of 4, and in this case the #1 quotient switch is closed.

The depression of the equals (z) key, for starting the division operation, completes a circuit to the quotient switches ISO-I60 described above in connection with Fig. 2 to enable the one of these switches to control thenumber of cycles of operation of the actuators. Theequals key also initiates operation 01 the quotient pre-estimating mechanism for closing a selected one of these quotient switches, and furthermore initiates operation of the dividend sign determining mechanism.

The actuation control circuit includes two switches 913 and I269 (Fig. 20) the closure of which by depression of the equals key, completes said circuit from main line 9, connected to switch I269, lead 9| Ia, switch 9I3, the normally closed switch 686, and the common lead 692 connected to the quotient switches ISO-I60, At the same time the above circuit is closed, a sign determining circuit is also closed by the sign determining mechanism. Assuming for purposes of illustration that the sign of the dividend register is positive, then the sensing of a positive value in the dividend register causes a switch 259 (Fig. 20) to remain closed and closes a circuit from lead 9| Ia through a solenoid 9I6 to ground. Energization of solenoid 9H5 moves the gang switches -800 from the upper positions shown to their lower dotted line positions.

Assuming further that a 4 quotient digit is pre-estimated, then the closure of the number 4 quotient switch I54 completes the above circuit from buss 692 through the closed number 4 quotient switch I54, switch leaf 196 (which is in its lower dotted line position) to lead 924, the actuating winding 8541) of the quotient magnet 854, lead 693, through the setting clutch solenoid-93 brand the: normallyv closed switches l 9m and 648 to ground; Thisucauses energization of :5 both the quotient magnet 854mandcthersettingH.

clutch 'solenoid 93i, thetlatter of which start: the

operationmof the division mechanism described.

hereinafter;

The mechanism that is controlled by the quo tientsolenoids for' determining the number of actuator cycles is substantially" the same: as the corresponding mechanism in -the above rnen-v tioned': Patent No. 2,567,120; the only difference being-that the mechanismin the present applica-- tion is adjustable to-ten different positions under to cause-disengagement of the main clutch and stop-the actuators after operation thereof. through'a number of cycles corresponding to the quotient digit estimated:

With the provision of ten actuation control magnets'representingthe quotient digits l to 10, a quotient of 99 may be registered by tencycles of positive" advance of the tens order quotient numeral wheel-and 'one negative cycle In the absence'ofthe in the units order quotient numeral -wheel-, 1. e. (10 X 10)"l:99; actuation control magnet 860; nine cycles of positive advance would b'e'required" inboth the tens and the units orders-to obtain a quotient of 99. Obviously, a quotient e150 be hundreds order quotient numeralwheel' and a single digitsubtraction: in the units order nu-" meral wheel, i. 5100 1299. "The present ma'-'" chine, however, "has been designed to start division operations with'the highe'st'order of the This mechanism:

.40 obtained by a singlej'digit of 'advanceof the divisor in alignment with the'highest orderu of the dividend, in which caseia pro-estimationv in the above mentioned hundreds order is not practical; therefore the firstdigit, of the quotient is notv short cut. llnlalloorders following. the.

first orden. however; the quotient is short-cut, andin .a quotient .of .5099; for example, .thellast,

three digits 099 are .determineclin the short-cut manner, i. e. by a single digit'of advance in thehundreds? orderand a single digit subtraction in the .unitsorder (100 1:99)

Dim'sor indicator provided with planetary: gearing ebetween'rthe three highest orders thereof for, compounding highest: divisor: orders is generally .indicatediat 463 in Fig; 10 andcorrespondssto a planetary gearing of the type disclosed in the :Patent' No: i r

2,343,273 issued Ma'reh '7, 1944; to 'whichrefer (Fig. -14) Thedivisoraindicator I02 (Figs 1 and. 10) .is

encei mayrbe: had for'sa detailed'descriptionof the-mechanisms.comprising the present divisor planetary mechanism. .A gear lfit is differentially irotated. according to the compounded divisor value, and drives through a double idler "Sea to rotate a gear I of the pre-estimation mechanism. Gear I65 (Figs; 10 and 16) is fixed to a shaft 'ltifi upon which the divisor indicator numeral wheels '2 3I are freely mounted.

It should be noted that the numeral wheels 23E of the divisor indicator always stand in full digital display position since each is rotated by a respective di ital input gear-of the planetary gearing witj and which input gear advances the numeral wheelindependently of the compounding mechanism as-describedin the last mentioned'patent.

A gear 1c) is integral with each numeral wheel 223i, and during division operations thegears 8420f the three highest divisor orders are locked against rotation to preventdisplaca ment'of the planetary gearing H53 when the value of the divisor is sensed. For this purpose a divisor lock-gate 66!, similar to one of the same reference numeral in the Patent No. 2,343,273, is provided to engage'the teeth of the'three highest order gearst'idii. The loclrgate ti ll is fixed to shaft Ed th which-is rocked counterclockwise by a lever S it-having connecting linkagee hiwwith a shaft This shaft, as described hereinafter, is moved clockwise by depression. of the division key and is maintained in clockwise position throughout the division operation. In this manner the-divisorloci; gatefiti is rocked countercloclzwise and the divisor indicator numeral wheels are held locked against rotation throughout the division operation.

Dim'sor sensing mechanism itiiiFig. 10) is rotated a selective amount according. to the compounded value of the three highest divisor orders. Cams Hand 58 (Fig. 2) 'are fixed to shaft ittand. therefore are rotated in accordance with said compounded'divisor value. These two cams are provided for alternatively controlling the setting of the divisor lever Hi2 along thedivisor scale as will'presentiy appeaigand for this purpose the'divisor lever M2 carriesitwo follower rollers 59 and lit for alternativelycontacting respecting cams i6! and W2. The movement imparted to theme-estimating mechanism'by thesetting of the divisor lever 542 along the divisor scale to a value greater than three is sufficient to render'negligible the effect of any inaccuracies or backlash in the pre-estimating mechanism due to manufacturing tolerances. Any such inaccuracy orbacklash how* ever, produce a greater error in quotient preestimation when smal divisor values are used for comparison; therefore when a divisor value from 1 'to 3'is used, both the divisor lever Hi2 and theldividend lever vI il are set along their respective divisor and dividend scales at values three times the values sensed. In this manner the mechanical movement of the ore-estimation mechanism is increased and the effect of the backlash is decreased without changing the ratio of thedividend tov the divisor.

v The previously mentioned. cam it controls the setting'of the divisor lever Hi2 along the divisor-scaiein accordancexwith the true divisor value-sensed, Whilethe cam I68. controls the setting ofthe divisor. lever'salongsaiclscale to a position equal to threei timesrthe yaluemf .the-di--..

From preceding sub-section it is seen that shaft 

